Silent Sound has turned the corner and we're heading south and towards home. Soon we will again cross the Arctic Circle, marking the official end of the Northwest Passage and an important milestone in our journey. But home is still a month of sailing away.

We are now sailing down the eastern Baffin Island coast, and we've had some stormy weather in recent days.

Now that we're out of the Arctic Archipelago and into the open sea, we will start seeing more icebergs, instead of ice floes. Ice floes are frozen seawater while icebergs are chunks of ice broken off glaciers in the High Arctic. Bergs begin as snow falling on land, which is then compressed into ice. Even though icebergs can be 20 or 30 metres high, most of their volume is below water. This means you have to stay well clear of them because they may spread out under water, like an upside down mushroom.

Dr Chris Pielou, our scientific adviser, tells me that icebergs contain vast numbers of very tiny bubbles, air that was trapped among the flakes of the snow from which the ice originated. This is what makes icebergs white. A chunk of berg-ice fizzes if you put it in water as the ice melts and releases these air bubbles.

For the crew of Silent Sound, icebergs are safer than ice floes because they are easier to see. Icebergs can be several stories high, and we can see them from miles away. We can easily avoid them, even at night. Ice floes, however, are low and flat on the water, and are very hard to see. If we hit one of these chunks of ice in the dark, there is a good chance we'd sink the boat. So, as you can see, we're on our way home, but still a long way from being safe and sound.